The present invention relates to an optical tomograph and an optical tomographic method, especially relates to optical tomographic technique that visualizes the distribution in an optical tomographic direction of a substance to be examined.
Recently, optical coherence tomography (OCT) that forms images showing a superficial shape and an internal shape of a measured object using light beams from a laser and others attracts attention (refer to Medical Photonics No. 1 (2010), pp. 29-33 and Medical Photonics No. 7 (2011), pp. 58-64). As OCT has no invasiveness into a human body differently from X-ray CT, the development of application in a medical field and a biological field especially is expected. For example, in an ophthalmic field, a device that forms images of an eyeground, a cornea and others is being realized.
In such OCT, spectrum-domain OCT is adopted. In the spectrum-domain OCT, as a reference mirror is not required to be driven in measurement differently from conventional type time-domain OCT, high-speed measurement is possible. In the spectrum-domain OCT, for example, an ophthalmoscope that acquires various information in a direction of the depth of an examined eye by radiating near infrared measurement light of short coherence length, that is, measurement light having a broad-band wavelength spectrum toward the examined eye, diffracting interference light into each wavelength component using a diffraction grating and others after its reflected light is made to interfere with reference light, instructing a light receiving element to receive diffracted luminous fluxes and analyzing their received signals is known (refer to Japanese Unexamined Patent Application Publication No. 1999-325849). The realization of a function that presents effective information in medical diagnosis by extracting the information of specific structure such as a blood vessel from three-dimensional tomographic image data by signal processing utilizing such high-speed OCT and plainly displaying this is expected.
In the meantime, for a method of measuring the distribution of a blood vessel using spectral information, a method (Narrow band imaging (NBI)) of sensing a hemoglobin component included in a blood vessel by diffracted light, roughly distinguishing the depth of the blood vessel and visualizing it and a method (Hemoglobin index: IHb) of measuring the local density distribution of hemoglobin are known. As for NBI, refer to Japanese Patent No. 3559755 and as to IHb, refer to Japanese Unexamined Patent Application Publication No. 1998-210454.
Further, for an example of a diagnosis system that combines results acquired in OCT and a blood analyzer by image processing, Japanese Unexamined Patent Application Publication No. 2012-10776 exists.